The muscles in the medial compartment of the thigh are collectively known as the hip adductors. There are five muscles in this group; gracilis, obturator externus, adductor brevis, adductor longus and adductor magnus.

All the medial thigh muscles are innervated by the obturator nerve, which arises from the lumbar plexus. Arterial supply is via the obturator artery.

Adductor Brevis

Fig 1.1 – View of the medial thigh, with the course of the obturator nerve highlighted

The adductor brevis is a short muscle, lying underneath the adductor longus.

It lies in between the anterior and posterior divisions of the obturator nerve. Therefore, it can be used as an anatomical landmark to identify the aforementioned branches.

Attachments: Originates from the body of pubis and inferior pubic rami. It attaches to the linea aspera on the posterior surface of the femur, proximal to the adductor longus.

Actions: Adduction of the thigh.

Innervation: Obturator nerve (L2-L4).

Obturator Externus

This is one of the smaller muscles of the medial thigh, and it is located most superiorly.

Attachments: It originates from the membrane of the obturator foramen, and adjacent bone. It passes under the neck of femur, attaching to the posterior aspect of the greater trochanter.

Actions: Laterally rotates the thigh.

Innervation: Obturator nerve (L2-L4).

Gracilis

The gracilis is the most superficial and medial of the muscles in this compartment. It crosses at both the hip and knee joints. It is sometimes transplanted into the hand or forearm to replace a damaged muscle.

Attachments: It originates from the inferior rami of the pubis, and the body of the pubis. Descending almost vertically down the leg, it attaches to the medial surface of the tibia, between the tendons of the sartorius (anteriorly) and the semitendinosus (posteriorly).

Actions: Adduction of the thigh at the hip, and flexion of the leg at the knee.

Fig 1.2 – Cross section of the inferior thigh, showing some of the medial thigh muscles. The adductor brevis and obturator externus attach superiorly in the thigh, and so are not visible in this cross-section.

Clinical Relevance: Injury to the Adductor Muscles

Strain of the adductor muscles is the underlying cause of what is colloquially known as a ‘groin strain‘. The proximal part of the muscle is most commonly affected, tearing near their bony attachments in the pelvis.

Groin injuries usually occur in sports that require explosive movements or extreme stretching. Treatment of any muscle strain should utilise the RICE protocol – rest, ice, compression and elevation.

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